• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.361-366
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• 2013

An imaging technique to visualize the internal defects in a plate-type nuclear fuel specimen was developed by using an active optical interferometer for a nondestructive quality inspection. A periodic thermal wave having a sinusoidal intensity pattern induced a periodical strain variation for the specimen. The varying strain image was acquired using an optical laser interferometer. The strain distribution over the internal defects will be distorted in an acquired strain image because a part of the thermal wave will be reflected from these defects during propagation. In this paper, internal defects were efficiently visualized by sequentially accumulating the extracted defect components. The experimental results confirmed that the developed visualization system can be a valuable tool to detect the internal defects in plate-type nuclear fuel.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.699-706
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• 2001

Waterproofing materials should be expected to last the life of the structure. An approximate life cycle cost should be to compare different materials based on initial and periodic repair / maintenance costs. Waterproofing applicators like materials that are easy to set up and clean up. The designer should choose a material that can be applied in almost all conditions. Design Professionals should specify independent inspection on critical jobs or in all cases where the budget permits. The basic causes of defection occurred during construction should be minimized.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.142-147
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• 2018

Private electrical facilities are judged whether it is suitable for the insulation aging condition of their incoming underground cables using DC leakage current test method. In the case where the service point of utility is the secondary side of cut out switch installed in the electric pole, there is a problem that it is difficult to separate the lightning arresters(LA) because of their high position of the pole. Therefore, the field test voltage is applied at value lower than DC 30 kV, which are stated in the inspection guideline. However, this test could reduced the insulation performance of the LA by accelerating the electrical stress of the metal oxide varistor element in the pre-breakdown region. In this study, we analyzed the relationship between the DC test voltage and the leakage current using the non-destructive DC high voltage equipment with leakage current measurement function. The results show that the leakage current increases sharply above the specified test voltage. As a consequence, it could be contributed to improve insulation aging inspection method by selecting the possible test area on the VI characteristic curve of the pre-breakdown area of the LA.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.127-138
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• 2011

Certified Missile Round Concepts that is one-shot device use the periodic inspection policy to improve the continuously deteriorated reliability. In this paper, we suggest dormant reliability prediction model by simulation with real operational environment. The suggested prediction model is based on optimal inspection period decision model and additionally considers various constraints; moving, inspection or repair service time. The simulation results show the constraints affect dormant reliability and missile availability. Lastly, we suggest building up a depot to resolve the above problems by the suggested simulation model.

• Journal of Soil and Groundwater Environment
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• v.21 no.4
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• pp.1-9
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• 2016

Rehabilitation for low-yielding wells resulting in improvement on groundwater quantity and quality is considered to be the most economic and ecofriendly method against the increasing demand to groundwater due to frequent drought and the increase in numbers of agricultural complex for growing horticultural crops. This study suggests standard, stepwise diagnostic fuctions consisting of four steps (Basic inspection, Specific inspection, Rehabilitation, and Management) for an optimal management to the wells. Basic inspection can provide information on current groundwater quantity and quality compared with those on its initial stage. Specific-inspection based on hydrogeology can scientifically demonstrate causes of deterioration on groundwater quantity and quality. Results of specific inspection can suggest an optimal rehabilitation method to solve deteriorating problems including clogging and corrosion for the wells. After rehabiliating the wells, an assessment on groundwater quantity and quality would be conducted to identify the suitability of the applied method and improvement of the wells. A short-term, periodic management to the wells is considered as the key to save a public management budget. Suggested diagnostic functions can possibly induce sustainable supply of agricultural groundwater to the farm land and finally contribute the increase on rural household income.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.1-8
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• 2017

A method for inspecting defects in display substrates utilizing Fourier optics is proposed in this paper. A cost-effective inspection system can be realized with the proposed method, because it does not require a high-magnification microscope. Also, the proposed method can avoid tight tolerance for variations in displacement between substrate and camera, which is stems from shallow depth of field of the high-magnification microscope. In addition, possible damage caused by collisions between substrate and the inspection equipment can be avoided. The decision algorithm can be simpler than for a conventional inspection system, because spatial shift of periodic substrate patterns does not affect the intensity distribution of the diffracted light, by the Fourier transform property. The proposed method is explained with numerical studies, and experiments are carried out to check its feasibility for color-filter substrates of a liquid-crystal display.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.60-67
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• 2016

A pressurized heavy water reactor (PHWR) designed to refuel in service produces the energy required by nuclear fission. The fuel channel consists of components such as a pressure tube which directly contacts the fuel and is a passage for the reactor coolant, a calandria tube which contacts the moderator and is rolled joint with calandria, and a spacer which is not to contact the pressure tube and a calandria tube. As the fuel channel is one of the most important equipments, it requires accurate and periodic inspections to assess the integrity of a reactor in accordance with CSA N285.4. A fuel channel inspection system is developed to inspect fuel channels during in-service inspection in Wolsong unit. In this paper, the results and considerations of a field test are presented in order to show the effectiveness of the developed fuel channel inspection system.

• Smart Structures and Systems
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• v.31 no.4
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• pp.335-349
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• 2023

Bridges constantly undergo deterioration and damage, the most common ones being concrete damage and exposed rebar. Periodic inspection of bridges to identify damages can aid in their quick remediation. Likewise, identifying components can provide context for damage assessment and help gauge a bridge's state of interaction with its surroundings. Current inspection techniques rely on manual site visits, which can be time-consuming and costly. More recently, robotic inspection assisted by autonomous data analytics based on Computer Vision (CV) and Artificial Intelligence (AI) has been viewed as a suitable alternative to manual inspection because of its efficiency and accuracy. To aid research in this avenue, this study performs a comparative assessment of different architectures, loss functions, and ensembling strategies for the autonomous segmentation of bridge components and damages. The experiments lead to several interesting discoveries. Nested Reg-UNet architecture is found to outperform five other state-of-the-art architectures in both damage and component segmentation tasks. The architecture is built by combining a Nested UNet style dense configuration with a pretrained RegNet encoder. In terms of the mean Intersection over Union (mIoU) metric, the Nested Reg-UNet architecture provides an improvement of 2.86% on the damage segmentation task and 1.66% on the component segmentation task compared to the state-of-the-art UNet architecture. Furthermore, it is demonstrated that incorporating the Lovasz-Softmax loss function to counter class imbalance can boost performance by 3.44% in the component segmentation task over the most employed alternative, weighted Cross Entropy (wCE). Finally, weighted softmax ensembling is found to be quite effective when used synchronously with the Nested Reg-UNet architecture by providing mIoU improvement of 0.74% in the component segmentation task and 1.14% in the damage segmentation task over a single-architecture baseline. Overall, the best mIoU of 92.50% for the component segmentation task and 84.19% for the damage segmentation task validate the feasibility of these techniques for autonomous bridge component and damage segmentation using RGB images.

• The KIPS Transactions:PartD
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• v.10D no.4
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• pp.727-734
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• 2003

Recently various quality assurance activities have been applied in software industry for the purpose of software qualify improvement, and the ultimate target of those activities are focused on removing defects from its developed applications. We declared "ZERO DEFECT 21" movement on March 1999 whose purpose is to deliver defect-free applications to the customer. In this paper we would like to introduce the followings $\circled1$ Approaching Methods, $\circled2$ Achievements of "ZERO DEFECT 21". After accomplishing first you of "ZERO DEFECT 21" movement which consist of Audits and Software inspections, we could get the following improvement . $\circled1$ due to conducting the "Audits," we could prevent 22 cases of customer claims, enhance 11.7% of design quality and improve 23.3% of deliverable reusability : $\circled2$ also, due to conducting the "Periodic Sampling inspection and Final inspection," we could enhance 123% of defect rate compared with early stage of development and 247% of defect rate compared with previous yew. Based on the survey results, we could conclude that "ZERO DEFECT 21 " movement provides confidence to project team members and reliability to our customers.ce to project team members and reliability to our customers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3636-3643
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• 2011

To prevent the electrical accidents in the laboratory, we identify problems for periodic inspections of the electric field and develop a fuzzy inference system that can be practically applied to check items. Focusing on electrical safety in the lab environment, we draw check items that can be applied in common and develop a standard checklist that is consistent with the laboratory electrical safety and the periodic inspections. Using the standard checklist we select the items that may contain a linguistic ambiguity and define the membership functions for these items. We also have a safety rating defined by the membership function. Using these fuzzy variables we form the fuzzy rules in the form of 'If-Then' and develop a fuzzy inference system through the fuzzy engine. From this, electrical accidents could be prevented in advance continuously by managing the intelligent and efficient inspection and electrical safety to prevent the electrical accidents in the laboratory.